2006 New York Code - Emission Of Air Contaminant; Standard Smoke Chart.

 
    §  24-142  Emission  of  air contaminant; standard smoke chart. (a) No
  person shall cause or permit the emission of air contaminant of:  (1)  A
  density  which appears as dark or darker than number two on the standard
  smoke chart or of an opacity which obscures vision to a degree equal  to
  or greater than smoke of number two density on the standard smoke chart;
  or
    (2)  A  density which appears as dark or darker than number one on the
  standard smoke chart, but less than number two on said chart, or of such
  opacity as to obscure vision to a degree equal to or greater than  smoke
  of  number one density on the standard smoke chart, but less than number
  two on said chart, if such an emission continues  for  longer  than  two
  minutes in the aggregate in any sixty minute period.
    (b)  The density or opacity of an air contaminant shall be measured at
  the point of its emission, except: (1) When the point of emission cannot
  be readily observed, it may be measured at an observable  point  on  the
  plume nearest the point of emission; or
    (2)  In  the  case of air contaminant emitted from a source outside of
  New  York,  it  shall  be  measured  after   the   plume   crosses   the
  jurisdictional boundary of New York city.